1. Field of the Invention
The invention relates to a water-tight and gas-tight zip fastener and a method for forming having a bridge, a transitional section, and a continuous bead. More particularly the invention relates to a water-tight and gas-tight zip fastener where a port includes sealing rings which seal in compression to a slide side core and between opposing legs.
2. Description of the Related Art
One method for forming a related zip fastener is known from DE-C-41 29 191. There, a closed spiral zip fastener is coated by means of an extrusion process and subjected to a cooling section, whereby a lateral tensile force is applied to the zip fastener strips. Then, the zip fastener is separated for later processing.
An objective of the present invention is to create an improved method of manufacturing a water-tight and gas-tight zip fastener in which such a zip fastener can be produced cost-effectively by simple means and with a complete seal.
It is another objective of the present invention to provide a water-tight and gas-tight zip fastener which provides a double seal in a port around a slide.
It is another objective of the present invention to provide a slide in the zip fastener which applies compression to a bridge portion of a port and reliably seals the slide to the port to eliminate fluid and gas seepage around the slide.
According to the present invention, a closed zip fastener, consisting of two zip fastener strips with spiral-shaped plastic zip fastener halves, is manufactured by means of an injection molding process.
The zip fastener of the present embodiment is injection molded in sections using an incremental feed to form a contoured profile on one side of a matched pair of zip fastener strips.
At least during the injection molding process, a lateral tensile force is applied to the zip fastener strips, which after the molding process is complete operate to provide a tensile force on each other and compress the coated sections together to seal out gas and moisture.
According to the present invention, the coating material consists of a thermoplastic polyurethane. The coating, prior to the first separation of the zip fastener strips, is formed at least on the top of the zip fastener strips, and is pre-slit in an opening direction. Frequently, there may be minimal or no lower coating on the underside of the zip fastener strips, but a lower coating may be applied to the underside of the zip fastener strips to provide additional leak resistance and sealing.
In the zip fastener, spiral zip fasteners may be preferably used, but are not necessarily used. The spirals can alternatively be elastically connected with the zip fastener strips, each being provided with a core that is elastically deformable in lateral direction, away from an opposite spiral row during formation of the coating sections.
Preferably a cut for the pre-slitting between the contoured coatings is made by means of a cam control on at least one end, with the cutting depth being adjustable to aid in accuracy during formation.
According to a special embodiment of the invention, in a second injection molding process, an additional coating material is placed in the slit and/or at least one additional parallel slit, and if necessary, the pre-slitting is repeated.
Prior to the injection-molding process, the zip fastener is available as bulk stock. After the contoured coating is applied by injection molding to the zip fastener, the zip fastener is cut to certain lengths, and in a second injection-molding process, a port is injection-molded.
The port is designed as a continuous bead surrounding a port hole. At least one sealing lip for a slide core of a slide is provided in the port hole of the port. Farther up on the port on at least a top surface, a sealing ring or another form of sealing lip may be preferably arranged. Advantageously, the bead is decorated inside the port hole on an underside portion so that while the zip fastener is in an open state the decorated area can be seen and the open state noticed by an observer for safety.
The port is also provided with a transitional section, which in the present embodiment widens into the shape of a wedge, extending in the continuous bead from the contoured coating to the port, so that the legs of the slide can exert a greater lateral pressure on the bridge and transition sections in a closed state and press the sealing lips and sealing rings against the slide and prevent gas and water leakage.
Before, during or after cutting to length, the end of the zip fastener, to which the port is to be injection molded, must be provided with a profile that improves the connection between the now contoured and coated zip faster and the to-be-formed port. An example of this type which provides and aids strong connection during injection molding is a notch, but other designs are allowable.
After forming the port, bridge, transitional section, and continuous bead one on end of the zip fastener, an end stop is injection molded onto the other end of the zip fastener to act as a stop for the slide during an opening process.
Prior to coating, the zip fastener strips are beneficially provided with a precoating or lamination, whereby the precoating or lamination may reach bonding values of at least about 180 N/5 cm thereby allowing a strong bond between the zip fastener strips and the contoured coating. As is known in the related art, a bonding value of up to 180 N/5 cm, means that a continuous force of at least 180N must be applied to tear asunder a 5 cm welding between two weldable textile materials. In the present circumstances, bonding forces of at least about this amount dictate effective bonding between the injection molded (weldable) coatings and the two weldable textile materials (zip fasteners).
Additionally, prior to further processing and after the precoating, the zip fastener strips are first roughened and/or provided with a bonding agent before coating with the final contoured coating material.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.
Below, the invention is described in more detail by means of examples shown in the drawings as follows: